Carburetor



1953 R. H. STERNAMAN 2,823,021

CARBURETOR Filed Dec. 1.3, 1952 INVENTORQ A rive/ve- Y:

CARBURETOR Robert H. Sternaman, Romeo, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 13, 1952, Serial No. 325,780

12 Claims. (Cl. 261-59) This invention relates to carburetors for internal combustion engines and primarily to those designed for automotive use which are provided with a main fuel supply passage and an auxiliary fuel supply passage which is automatically caused to become operative under certain operating conditions to provide a somewhat richer than normal mixture under such conditions.

Most conventional carburetors in use at the present time are provided with fuel passages of the character referred to. When operating with a partly open throttle until the throttle approaches wide open position, a slightly leaner mixture is desirable than when operating withthe throttle in relatively wide open position, when full power is necessary. It has been found that in some installations of conventional carburetors of this type, the fuel mixture gets slightly too rich when both fuel passages are functioning, and the primary object of the present invention is to provide means for automatically preventing this occurrence. I

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

.Figure 1 is a horizontal. plan view of the carburetor which is shown in section in Figure 2; v Figure 2 is a vertical section on the line 2-2 of Figure 1;

'Figure 3 is a fragmentary vertical section on the line 33 of Figure '1;

' Figure 4 is an enlarged detail section of a part of the device as shown in Figure 3.

The carburetor in which the present invention is disclosed is fully shown and described in the copending application of Elmer Olson, Ser. No. 109,347 filed August 9, 1949, now Patent No. 2,694,560, dated November 16, 1954, Since the general construction of the carburetor is npt material, so far as the present invention is concerned, the details of construction will not be fully described -herein and reference maybe had to the application re- -ferred to for a full disclosure. thereof. Only those portions of the carburetor which are immediately, associated with the present inventionare described in, detailherein. A choke valve 4 is positioned in theair inletcasting 1 and issecured to a shaft 5 which is mountedfor. rotation in the castingl; The means for operatin g this valve is wholly immaterial, so far as the presentinventionis concerned, but the valve can be variably positioned by man- ,ual means to control the amount of air entering the carburetor, whereby a mixture richenough for starting purposes may be obtained and thevalve may then be opened after the. engine has started tovariably control the mixture during'the time the engine is warming up until, when normal temperature-is reached, the valve may be fully o erred so as to place no restriction upon the entering air. ln the casting 3 a manually operable shaft, 6 ;is suitably journalled for rotation and secured to this shaft in any Unite States Patent 0 "ice suitable way is a throttle valve 7 which may be variably positioned by any suitable manually operated means to variably control the quantity of combustible mixture which is supplied to the engine and in this manner to control the speed thereof.

As already stated, a constant level fuel chamber is formed within the casting 2 and to supply fuel to this chamber a fuel supply pipe (not shown), is adapted to be connected to a nipple 8 which is screwed into the air inlet casting 1 and communicates with a passage 9 formed therein. A nipple 10, having a fuel passage 11 formed therein is screwed into the casting 1 and fuel is adapted .to flow from the passage 9 through the passage 11 into the fuel chamber above referred to. A valve 12 controls the flow of fuel through this passage and such valve is engaged by a member 13, pivotally mounted on a pin 14, which is positioned in a bracket 15, extending downwardly into the fuel chamber from the casting 1. The member 13 which engages the valve 12, is connected in the conventional manner to a float (not shown), and is effective to maintain a constant level of fuel in the fuel chamber in the usual way.

Secured to the casting 1, in any suitable manner, and extending downwardly into the fuel chamber is a casting 16 in which is formed a vertical fuel passage 17, to which fueljs supplied from the fuel chamber through a main fuel supply passage formed in a calibrated plug 18, which is screwed into the lower end of the casting 16. At its upper end, when the parts are assembled as shown in Fig. 2, the passage 17 connects with a horizontal-passage 19 formed in a bridge member 19a, which is a part of the casting 1 and extends across the carburetor intake passage 20. This passage 19 supplies fuel to a main fuel inlet 21 which discharges fuel from the passage 19 into the mixture passage 20 and the fuel supplied by the main fuel inlet 21 is controlled by a bushing 22, which fits within the fuel inlet 21 and is provided with a small fuel feeding orifice 23 therein.

To the left of the main fuel inlet the bridge member 19a has a passage formed therein in which is fitted a tube 24 that receives fuel from the passage 19 and which discharges fuel in an enlarged space 25 in the bridge member. This space communicates with a vertical fuel pas sage 26 through which fuel is conveyed to fuel supply inlets that discharge fuel at a point in the intake passage adjacent the throttle valve 7, for operation of the engine at idling. The idling fuel supply inlets are not shown herein because the arrangement of such inlets forms no part of the present invention, but are shown and fully described in the copending application above referred to.

Immediately above the bushing 22 are a plurality of air inlet openings 27 which admit air for mixture with the fuel which is discharged by both the main and idling fuel inlets.

At theleft side of the intake passage as shown in Fig. 2 a cylinder 30 is formed in the casting 1 and when the parts are assembledas shown, such cylinder is in alignment with a similar. cylinder 31 which is formed in the fuel chamber castingv 2. Slidable'. in the cylinder 31 islpa piston 32which is. actuated by thethrottle through mechanism,. which is-not illustrated and-which needv not be described herein, for the purposeof supplying additional fuel to enrich the mixture for acceleration purposes. This piston is moved downwardly by.the throttle. upon rapid opening. movements thereof to force a quantity: of fuel into the intake passage to enrich the mixture as described and the cylinder 30 is incornmunication with the atmosphere through a vent tube 33,,Which is alsoin communication with' the space in the. fuel chamber above the fuel therein in orderto vent such chamber-and maintainin :th'e chamber a substantially atmospheric. pressure gig At the extreme left of Fig. 2' there is disclosed a lever 34 which is pivotally mounted on a boss projecting said Patent No. 2,694,560.

As stated previously, the main fuel supply passage 17 is supplied with fuel from the fuel chamber 2 by the passage formed in the calibrated plug 18 and this plug constitutes the sole means for supplying fuel to the passage 17 during most of the operation of the engine. However, when the engine is operating with a substantially wide open throttle, additional fuel is supplied to the passage 17 through the passage 40, which is best shown in Figs. 3 and 4 and which is formed in the same casting 15 in which the passage 17 is formed. The passage 4% communicates with a chamber 41, as shown in Figs. 3 and 4, and screwed into this chamber is an externally threaded plug 42 having a cylindrical recess 42a, in which is received a check valve 43 which is normally forced upwardly by a spring 44 to a position where it closes an orifice 45, formed in the wall of the casting 16 and connecting the small chamber 41 with the main fuel chamber formed in casting 2. Positioned in the passage in a slightly enlarged portion thereof is a calibrated plug 46 which has a tight fit with the walls of the passage and which is provided with an orifice 47, which controls the flow of fuel therethrough.

When the engine is inoperative, the valve 43 is moved downwardly to the position shown in Figs. 3 and 4 by a tube 48 which, in the position shown, projects through the opening to engage the check valve 43. This tube is secured at its upper end to a hollow piston 49 which is slidable in a cylinder 50 formed in the casting 1 and is pushed downwardly to the position shown when the engine is not running, by a spring 51, received within the hollow piston and positioned between the closed end of such piston and the upper end of the cylinder 50. The tube 48 is threaded in a bore 52 formed in the lower end of the piston 49 and an orifice 53 connects the bore 52 with the space in the fuel chamber above the fuel therein, this space being vented by the tube 33 which admits airto such space and maintains such space at substantially atmospheric pressure When the engine is operating at intermediate speeds with the carburetor throttle in a partly opened position, the piston 49 is moved upwardly against the pressure of the spring 51 by the effect of engine suction on the piston 49. To accomplish this movement of the piston, the cylinder 59 at its upper end communicates with a short passage 54 and the latter connects with a'horizontal passage 55 which in turn connects with a vertical passage 56, all of which are formed in the casting 1. At its lower end, the passage 56 connects with a groove 57 which is formed in the bottom of the casting 1 and communicates with a passage which extends to a point in the carburetor intake passage adjacent the throttle valve and posterior thereto so that the suction which is maintained in the intake passage at points between the throttle valve and the engine is communicated to. the groove 57 and through passages 54, 55 and 56 to the piston 50. The passages extending from the groove 57 to the intake passage are exactly the same as in the earlier application previously referred to an since the exact form of these passages is not material, such passages are not shown herein.

As the throttle is moved toward wide open position, the suction posterior to the throttle is reduced and the suction which is thus communicated to the piston 50 becomes insufiicient to overcome the force of the spring 51 and the latter moves the piston downwardly to the position shown in Figs. 3 and 4, thus moving the check valve out of its closed position and permitting fuel to flow from the chamber 2 into the chamber 41 and through the fuel feedingorifice '47 and passage 40 into the fuel passage 17 to' augment the supply offuel thus conveyed v to such passage throughthe plug 18. The extent of opening of the throttle when this action takes place is not constant, but will vary with the load. For example, if the vehicle on which the carburetor is used is ascending a hill and because of the heavy load the engine is running slowly, the throttle would be open to a lesser extent when the suction becomes insufficient to overcome the force of spring 51 than would be the case if the vehicle is operated on a level or going down-hill.

The structure described so far is substantially the same as that which is shown and described in aforesaid Patent No. 2,694,560, except for the fact that instead of employing the tube 48 to move the check valve 43 to open position when the throttle approaches its wide open position, a solid rod is employed for this purpose. With such a structure, in some installations the mixture supplied at relatively wide open throttle positions is slightly too rich and in order to prevent this condition the tube 48 has been substituted for a solid rod, according to the present invention. The orifice 53 admits air to the tube 48 from the space above the fuel in the fioat member. At its lower end such tube 43 has a notch 60 formed therein which provides a port'through which air from the interior of the tube may flow into the chamber 41 when the tube is in position to hold valve 43 open, as shown in Figs. 3 and 4. Obviously, when the tube is in this position, the notch 60 is subject to the suction maintained in the passage 17 and this suction causes a flow of air to take place from the space above the fuel in chamber 2 through the opening 53, downwardly through the tube 48 and through the port 60 into the chamber 41. This flow of air reduces the suction which is maintained within the chamber 41 and therefore reduces the amount of fuel which would otherwise be supplied'through the passage 4%, so that with the devicewhich is disclosed herein, the amount of fuel supplied through the auxiliary fuel supply means is not as great as when a solid rod is used to actuate the check valve 43.

Obviously, the amount of fuel supplied by the passage 40 can be varied by changing the size of the orifice 53 which admits air to tube 48. Also, instead of employing the slot 53 an orifice may be formed in the side of the tube adjacent the lower end and by variation in the size and shape of such orifice, the admission of air and the amount of fuel supplied can be modified. By adjusting the position of the tube 48 with respect to the piston 49 or by using a tube'of different length so that the'position of the lower end of the tube relative to the seat of the check valve is changed, the predetermined suction at which the opening of the valve is effected can be changed. In view of the foregoing, it should be apparent that with proper calibration, substantially any desired rate of fuel flow through the passages 40 can be obtained.

As shown in the drawings, the tube 48 is threaded on its outer-surface and screwed into the piston 49, but it will be-understood that such tube may simply have a tight press'fit in the bore 52, in which event the tube ismerely pushed into the bore to some predetermined position.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it isto be understood'that otherrforms might be adopted.

'What is claimed is. as follows:

1. 'A- carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and'fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture suppliediby said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel'passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, means for'automatically rendering said auxiliary fuel passage effective as the throttle is moved to rela tively wide open position, and'means for introducing air-into the auxiliary'fuel passage to control the flow effective whenever the fuel passage is rendered effective. 2. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage,

, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passageto the engine, a

fuel chamber, a main fuel supply passage for conveying 7 the auxiliary fuel passage whenever the valve is opened.

3. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, means operable in response to movement of the throttle to relatively Wide open position to open said valve and to introduce air into the auxiliary fuel passage whenever the valve is opened, and -means for-varying the admission of air in accordance with the opening of the valve.

4. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, and suction controlled means for opening said valve and for admitting air to said auxiliary fuel passage whenever the valve is open.

5. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, suction controlled means for opening said valve and for admitting air to said auxiliary fuel passage whenever the valve is open, and means for variably determining the degree of suction at which said air admitting means becomes operative.

6. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, suction controlled means for opening ,said'valve and for admitting air to said auxiliary fuel passage whenever the valve is open, means for variably'determining the degree of suction atwhich said air admitting'meansrbecomes operative, and means for varying the admission of air inversely with respect 'to the amount of suction effective on said suction controlled means.

7. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the .quantity of combustible mixture supplied by said mixture passage to the engine, a fuel'chamber, a main fuel supply passagev for conveying fuel from the fuel chamber tosaid fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and meansfor holding said valve closed during most engine'operation, a suction operated piston subject to the suction in the mixture passage posterior to the throttle valve and means operated by said piston for holding the fuel controlling valve open when the suction effective on the piston is less than some predetermined suction and for admitting air to said auxiliary fuel passage whenever the suction is less than such predetermined suction.

8. .A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber,-'main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, a suction operated piston subject to the suction in the mixture passage posterior to the throttle valve, means operated by said piston for holding the fuel controlling valve open when the suction effective on the piston is less than some predetermined suction and for admitting air to said auxiliary fuel passage Whenever the suction is less than such predetermined suction, and means for variably determining the predetermined suction at which the air admitting means becomes effective.

9. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating conditions, a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, a suction operated piston subject to the suction in the mixture passage posterior to the throttle valve, means operated by said piston for holding the fuel controlling valve open when the suction effective on the piston is less than some predetermined suction and for admitting air to said auxiliary fuel passage whenever the suction is less than such predetermined suction, and means for variably determining the amount of air admitted to the auxiliary fuel passage in accordance with the position of the piston.

10. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine,

a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying-fuel from said fuel cham- 'ber to said-fuel inlet under certain'operating conditions, fa valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, a suction operated piston subject to the suction in the mixture passage posterior to the throttle valve, and a tube connected to the fuel passage Whenever the tube is in position to hold the fuel controlling valve open.

11. A carburetor for an internal combustion engine having in combination a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage,

' a throttle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary 7 fuel passage for also conveying fuel from said fuel chamher to said fuel inlet under certain operating conditions,

a valve for controlling the flow of fuel through said auxiliary fuel passage and means for holding said valve closed during most engine operation, a suction operated a piston subject to the suction in the mixture passage posterior to the throttle valve, and a tube connected to the piston and movable thereby to a position to hold said fuel controlling valve open when the suction effective on said piston becomes less than a predetermined suction,

, said tube communicating with an opening relatively close to its point of connection with said piston to admit .air thereto and an opening adjacent its point of engagement with the fuel controlling valve to permit air to fiowtherefrom into-the auxilitry fuel passage whenever the valve is open.

12. 'A carburetor for an internal combustion engine having ill-,COIIlblIlEtlOll a mixture passage, air and fuel inlets for supplying air and fuel to said mixture passage, atthrottle valve for controlling the quantity of combustible mixture supplied by said mixture passage to the engine, a fuel chamber, a main fuel supply passage for conveying fuel from the fuel chamber to said fuel inlet, an auxiliary fuel passage for also conveying fuel from said fuel chamber to said fuel inlet under certain operating condi' tions, a valve for controlling the flow of fuel through said auxiliaryafuel passage and means for holding said valve closed during most engine operation, a suction operated piston subject to the suction in the mixture passage posterior to the throttle valve, and a tube connected to the piston and movable thereby to a position to hold said fuel controlling valve open when the suction effective on said piston becomes less than a predetermined suction, said tube being effective to convey air to the auxiliary fuel passage whenever thetube is in position to hold the fuel controlling valve open, and means for adjustingtthe tube relative to the piston in order to variably determine the predetermined suction at which the tube becomes effective to open the fuel controlling valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,603,466 Anderson July 15, 1952 2,751,201 Heftler June 19, 1956 

